The invention relates, generally, to public safety communication systems such as 9-1-1 emergency service and, more particularly, to a system for providing enhanced 9-1-1 capabilities in wireless communication systems.
It will be understood that emergency service is widely provided as 9-1-1 service where a caller can reach emergency services such as police, fire, ambulance or the like by dialing 9-1-1. Enhanced 9-1-1 service provides the entity responsible for handling the emergency call, commonly referred to as the public safety answering position (PSAP), with the calling party's location, telephone number and other information related to the calling party. Providing this information to the PSAP enables the PSAP to locate the calling party even if the calling party is unable to identify his or her location and to reestablish contact with the calling party even if the original emergency call is terminated. Thus, the ability of a communications system to provide enhanced 9-1-1 service dramatically improves public safety.
In the typical land line 9-1-1 service application, an automatic number identification (ANI) is associated with each customer line such that there is a one to one relationship between ANI numbers and customer locations. When a calling party's 9-1-1 emergency call is forwarded to the selective router switching system serving the 9-1-1 call, the call set up message includes the ANI number. An ANI data base, accessible by the selective router switching system, maintains a mapping of ANI numbers to emergency service zones. Specifically, the geographic area served by the switching system is divided into emergency service zones (ESZs) where each ESZ encompasses a portion of the customers hosted by the switching system. Thus, every ANI number is correlated with one of the ESZs although each ESZ serves many ANI numbers. The switching system, after identifying the appropriate ESZ from the ANI data base, forwards the emergency call to the PSAP responsible for that ESZ. The ANI number is also forwarded to the PSAP in the call set up message. The PSAP accesses an automatic location information (ALI) data base where customer information such as customer's name, physical location such as address or latitude and longitude, telephone number and the like can be retrieved based on the ANI number. Once the PSAP obtains this information, it can direct emergency services to the appropriate location, call back the calling party if disconnected and otherwise provide enhanced services.
While the above-described system works well for land line telephones, it is not possible to process emergency calls from mobile wireless devices in the same manner. Because mobile wireless communication devices are by definition not tied to a particular customer location, an ANI number for the mobile device cannot be translated to the present location of the device (the ANI number for a mobile device is typically correlated to the customer's billing address). As a result, efforts have been made to provide enhanced 911 service for mobile communication devices. One such system uses a location detection device that is capable of locating the latitude and longitude of a mobile caller by triangulating on the 9-1-1 signal transmitted by the mobile device. A data link between the location detection device and the ALI data base allows the latitude and longitude to be transmitted from the location detection device to the ALI data base where it can be retrieved by the PSAP. While such a system can be effective it requires that a location detection device be located near all cell sites and that a data link be established between each location detection device and with the ALI serving the relevant PSAP. Moreover, because the information is transmitted outside of the call set up sequence and public switched telephone network, communication between the location detection device, the mobile switching center, the ALI and ANI data bases, the switching system and the PSAPs must be administered and coordinated. Thus, implementation of the system is expensive and resource intensive.
Thus, an improved system for providing enhanced 9-1-1 service in wireless communication systems is desired.